Abstract 4470: Elucidating the role of drug-linker hydrophobicity in the disposition of antibody-drug conjugates

Abstract

Abstract The in vitro potency of antibody-drug conjugates (ADCs) is generally proportional to the level of drug loading, with higher drug per antibody levels producing more potent ADCs. However, this intuitive relationship often fails to translate in vivo, presumably because plasma clearance of the ADC also increases with drug loading, resulting in substantially reduced exposure to highly loaded ADCs (Hamblett, KJ et al, Clin. Cancer Res. 2004, 10: 7063-7070). We postulated that this accelerated clearance effect is not purely a function of the number of drugs per antibody, but also of the intrinsic hydrophobicity of each drug-linker. Collectively, drug-linker hydrophobicity and number of drugs per antibody determine the overall hydrophobicity of the ADC. To test this hypothesis, we designed and prepared a series of drug-linkers within the auristatin class that varied in hydrophobicity, and used them to produce a corresponding series of homogeneous 8-loaded ADCs. The pharmacokinetic profiles of these ADCs were determined and found to correlate well with their relative retention times by hydrophobic interaction chromatography. We further postulated that hydrophobicity-driven clearance is likely to be mediated by cells of the mononuclear phagocytic system (MPS). To identify the specific cell populations responsible for accelerated ADC clearance, we performed an immunohistochemistry-based biodistribution study which has provided clear evidence for the cellular sites of hydrophobic ADC clearance which are not operative on native antibodies or hydrophilic ADCs. Using the information gained from these studies, we have successfully prepared a hydrophilic auristatin drug-linker which enables the preparation of ADCs uniformly loaded with 8 drugs per antibody at defined cysteine sites. These ADCs evade clearance by the MPS, maintain native antibody pharmacokinetics, and translate their high in vitro potency into the in vivo setting. Citation Format: Svetlana O. Doronina, Jocelyn R. Setter, Tim D. Bovee, Martha E. Anderson, Mechtild Jonas, Steven Daniho, Heather Kostner, Peter D. Senter, Robert P. Lyon. Elucidating the role of drug-linker hydrophobicity in the disposition of antibody-drug conjugates. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4470. doi:10.1158/1538-7445.AM2014-4470